Composite baseball bat with cavitied core

ABSTRACT

A baseball bat or the like comprises a tube formed with an outer layer of cellulose material covering a layer of fiber reinforced resin, with the tube layers being impregnated with and bonded to one another with a cured resin. The outer layer of the bat consists of one or more strips or sheets of cellulose material such as paper or wood. Cellulose fibers tend to stretch when deformed by the ball impact so as to spread the impact over a number of fibers and exhibit a high compressive strength. Therefore, they may be effectively utilized as the outer layer of the bat. The tube preferably has a foam core including a central cavity lined with a layer of fiber reinforced resin, said core having sufficient resiliency to allow the tube to resiliently deform during impact with a baseball. Bat performance may further be improved by adding an internal layer of fiber reinforced resin to the interior of the foamed core. The product is formed by molding over a form which may constitute the cavitied foam core or, alternatively, a forming mandrel which is removed after the resin is cured. The cavity may be filled with a material which is less dense than the core.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 08/262,432,filed Jun. 20, 1994, U.S. Pat. No. 5,459,330, which is, in turn, acontinuation-in-part of U.S. Ser. No. 137,694, filed Oct. 15, 1993, U.S.Pat. No. 5,460,369 which is, in turn, a continuation of U.S. Ser. No.883,263, filed May 14, 1992, abandoned, which is, in turn, acontinuation-in-part of Ser. No. 518,782, filed May 4, 1990, and nowU.S. Pat. No. 5,114,144.

FIELD OF THE INVENTION

This invention relates to baseball bats or the like comprising acylindrical tube of cellulose material overlying a fiber reinforcedresin layer and a central core, with the resin impregnating thecellulose material and adhering it to the fiber reinforced resin layer.

BACKGROUND OF THE INVENTION

Baseball bats and like articles are traditionally made of solid wood.These articles are relatively expensive and frequently break in use.Moreover it is difficult by natural limitations to design these productsso that they will have sufficient strength as well as functionalproperties such as weight, balance and flexibility to resist breakage.As a result of these deficiencies, extruded tubular aluminum bats havebeen recently extensively used for baseball and softball games but havenot adapted for professional play because of limitations on weight,strength, sound, performance and the traditional aesthetic preferencefor wood.

It is accordingly an object of the present invention to provide baseballbat which utilizes cellulose materials, such as wood veneer or paper, asthe laminate outer layer of the bat designed to complement and work withan inner layer or layers of synthetic reinforcing material and a centralcore. This composition produces an engineered composite with the desiredweight, strength, stiffness and flexibility to produce a bat with moredesirable performance characteristics and a longer life than either thesolid wood or extruded bats.

SUMMARY OF THE INVENTION

The present invention is directed to articles such as bats, drum sticks,billy clubs, cricket bats, field hockey sticks, furniture legs or thelike, formed of cylindrical tubes. The preferred embodiment of thepresent invention takes the form of a baseball bat which tapers from arelatively narrow handle section into a larger diameter, bulbous, barrelsection. The outer layer of the bat consists of one or more strips orsheets of cellulose material such as paper or wood. Cellulose fiberstend to stretch when deformed by the ball impact so as to spread theimpact over a number of fibers and exhibit a high compressive strength.Therefore, they may be effectively utilized as the outer layer of thebat. A single cellulose sheet may be employed, in which case the grain,if any, of the sheet is preferably arrayed parallel to the longitudinalaxis of the bat. If a plurality of cellulose sheets with grain, such aswood veneer, are used, their grains are preferably crossed relative toone another. Alternatively, strips of cellulose may be wound around inspiral fashion to cover the bat. Moreover, I discovered that adding aninternal layer of fiber reinforced resin to the interior of thepartially hollow foamed core improves bat performance.

In another embodiment, the cellulose layer is formed by cutting a pairof longitudinally extending sections of appropriately varying width,optionally imprinting, etching or embossing the sections to produce awood grain effect and optionally a logo, and pre-shaping the sectionsthe into semi-cylindrical configuration by soaking them with solvent andthen shaping them in dies while a solvent is driven off by heat.

The veneer layer formed of these two preshaped sections overlies and isadhered to a tubular layer formed of multiple sheets ofresin-reinforced, high tensile strength fiber fabric such as glass,carbon, ceramic or Kevlar®. The fiber orientations of the multiplelayers are angled relative to one another. The fiber sheets may beknitted, woven or otherwise formed and are preferably formed as atubular sock by edge seaming two longitudinally aligned sections. A pairof the socks, with their seams displaced by 90° relative to one anotherare arrayed over a shaped form which may either constitute a mandrill tobe later removed or a permanent foam core for the bat. The fiber fabricis then coated with resin in liquid form, or preimpregnated fabric maybe used, and the two veneer sections are positioned over the fabric. Theresin is then cured while the veneer is pressed against the fiber layereither by means of a vacuum bag or matched dies. In one embodiment ofthe invention, employing a removal mandrel as a form, curing isaccelerated by heating the formed composite at a suitable curingtemperature for the resin. When the composite is formed over the foamplastic core, the curing temperature must be limited to prevent damageto the core.

After curing over a mandrel, the mandrel is removed, a preformed knobend is fitted over the open handle end of the tube, a preformedfiberglass cap is fitted over the barrel end, and both are adhered tothe tube with resin. In one embodiment of the invention, a self-foamingplastic resin compound, preferably a urethane, is injected into the tubethrough a small hole in one of the bat ends. The two components of theresin react within the tube, filling the tube with a foamed core. Thefoamed in core may be partially hollowed out to form a core having acentral cavity. The central cavity may be left hollow, or may be fittedwith a second type of foam of a different (lower) density. Preferably,the volume of urethane components injected is varied along the length ofthe tube to create a higher density foam at the barrel end than at thehandle end, shifting the center of gravity of the bat toward the barrelend. In the preferred embodiment, an internal layer of fiber reinforcedresin is added to the foamed core by using a fiber sock and arraying itover the mold on which the foam core is formed or by adhering it to theinterior of the foam core after it is formed. When the resin impregnatedouter tubes are cured directly over a foamed core, the handle end isfitted with a preformed knob and the barrel end with a preformed cap.

Alternatively, the core may be first molded in a suitable mold andcovered with the fiber fabric sock and liquid resin prior to attachmentof the veneer layer. The knob and end cap may be formed in the same moldby injecting either a heated thermoplastic with an appropriate fillersuch as ground fiber as wood flour or a two-part reactive resin such asepoxy, with or without a filler. The core may be formed with a molded-in(or otherwise formed, such as by hollowing out) central cavity, eitherempty or filed with a lower density material. Preferably, the centralcavity radially extends from the longitudinal axis of the bat andextends longitudinally along at least a portion of the bat. The barrelof this embodiment of the bat may be made relatively larger with respectto the handle.

In the embodiments of the bat with foamed cores, the density of the foamis limited so that when the bat impacts a pitched ball, the tubularouter layers deform inwardly, locally compacting the core. The samelocalized deformation occurs with a hollow core bat formed in accordancewith the present invention, but the hollow core bat also undergoes alarger hoop, radial distortion. The embodiment including the core withthe central cavity undergoes a combination of local spring deformationand hoop, radial deformation. By adjusting the size of the centralcavity, selecting the material of which the core is formed, and choosingwhether or not to fill the central cavity with another material, therelative amounts of the two types of deformation may be changed,resulting in different performance characteristics. Thus, the bats ofthe present invention may be made to completely simulate the performanceof a solid wood bat (which undergoes virtually no local deformation) or,alternatively, exceed the performance of the livelier aluminum bats withtheir larger sweet spots.

Other objectives, advantages and applications of the present inventionwill be made apparent by the following description of several preferredembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The description makes reference to the accompanying drawings in which:

FIG. 1 is a perspective, exploded, partially broken-away view of a bat,representing a preferred embodiment of the present invention;

FIG. 2 is a sectional view through the bat of FIG. 1 taken along line2--2 of FIG. 1;

FIG. 3 is a sectional view through an alternative embodiment of the bathaving a hollow core;

FIG. 4 is a partial, longitudinal cross-sectional view through the knobend of the bat of FIGS. 1 and 2, illustrating the knob end cap;

FIG. 5 is a partial longitudinal cross-sectional view through the barrelend of the bat of FIGS. 1 and 2 illustrating the barrel end;

FIG. 6 is a side view of a section of wood veneer, cut to form one ofthe two sections used to cover the outer surface of the bat andimprinted with the logo required on the finished bat;

FIG. 7 is a perspective view of a veneer section after it has beenpreshaped for use in forming the bat of the present invention;

FIG. 8 is a view of multiple ply, knitted high tensile fiber fabricsheets cut to form a sock for use in forming the bat of the presentinvention;

FIG. 9 is a perspective view of a multi-ply, high tensile fiber fabricsock formed by sewing together two stacks of cut fabric sheets, for usein forming the bat of the present invention;

FIG. 10 is a sectional view through a resin-impregnated tube of woodveneer overlying a fiber sock, within the female dies used to form batsof the present invention;

FIG. 11 is a sectional view of a cured bat tube formed in accordancewith the present invention, with a knob fitted at the handle end, in theprocess of having self-foaming, liquid resin components being injectedinto the tube to form a foam plastic core by a foam-in-place technique;

FIG. 12 is a sectional view through another embodiment of the bat havinga core with a central cavity;

FIG. 13 is a sectional view through the bat of FIG. 12 taken along lines13--13 of FIG. 12; and

FIG. 14 is a sectional view through another embodiment of the bat havinga foamed in core with an internal layer of fiber reinforced resin.

DETAILED DESCRIPTION OF THE INVENTION

While the present invention is not limited to baseball bats, and extendsto similar articles such as drum sticks, billy clubs, cricket bats,field hockey sticks, furniture legs and the like, a bat constituting anembodiment of the invention is illustrated in FIGS. 1 and 2. The bat,generally indicated at 10 in exploded form, consists of a tube 12, ahandle knob generally indicated at 14 and a barrel cap generallyindicated at 16. The tube 12 has an outer configuration and dimensionslike those of conventional prior art bats which are formed of solidwood, aluminum tubing, or fiber reinforced resin. The bat is radiallysymmetrical about a centerline, and tapers from a relatively narrowhandle end 18 to a larger diameter, bulbous, barrel end 20.

The outer surface of the bat is covered by a cellulose material 22 suchas wood veneer, paper, or thin cardboard, which may be preprinted,embossed or etched with an appropriate decorative design such aswoodgrain and/or a logo, and coated and impregnated with a cured epoxyresin. In an embodiment of the invention, the cellulose material 22 isan veneer sheath that is formed of two longitudinally array strips or`planks` of white ash veneer of approximately 1/8 to 1/16 inchthickness. The term `plank` is used because the strips vary in widthlongitudinally so that when they are laid in side-by-side abutment withone another they form the outer contour of the bat without overlap. Thestrips are preferably laid with their grains extending longitudinallyalong the length of the bat to provide the maximum longitudinal tensilestrength and impact resistance. In other embodiments, each plank may beformed of a plurality of thinner sheets of wood veneer with their grainspreferably arranged at angles to one another. In yet other embodiments,the sheath may be formed of thin strips of veneer which are spirallywound onto, or otherwise applied to, the bat.

The cellulose outer surface 22 overlays a fabric layer of high tensilestrength, resin impregnated, fabric socks 24a, 24b. Only two socks areshown for purpose of illustration although a greater or lesser number ofsheets may be used in alternative embodiments of the invention. Thefabric layer surrounds a core 28 formed of a resilient urethane foam orthe like. As will be subsequently described in detail, the core may varyin density over the length of the bat, preferably with a higher densitysection adjacent the barrel end 20 to shift the center of gravity of thebat toward the barrel end and improve the impact strength of the barrel.

The handle end of the bat, illustrated in detail in FIG. 4, is closedoff by the knob 14 which includes an extending cylindrical section 30which is of the same outer diameter as the handle end 18 and abuts thetermination of the wood veneer sheath 22. The knob end 14 may be formedof plastic, solid wood or a combination thereof, and may be integralwith the rest of the bat 10 by molding in a process which will besubsequently described.

Similarly, as illustrated in detail in FIG. 5, the barrel end of thetube 20 is terminated by the cap 16, preferably formed of fiberreinforced resin, which has a rounded end 32 and a tubular section 34with an outer diameter which mates with the inner diameter of the fibersections and is adhered thereto by resin. This end can also be formed inthe mold with the bat.

Alternatively, the bat may be formed with a hollow core rather than asolid core 28. A cross-sectional view of this alternative embodiment ofthe invention is illustrated in FIG. 3, generally at 40. The hollow corebat may otherwise be substantially identical to the solid core bat,although to achieve the same weighing, it is necessary to use heaviercloth socks 24a, 24b. A hollow aluminum core could also underlie theresin impregnated fabric layer.

One of the planks of wood veneer suitable in forming the bat isillustrated in FIG. 6. The veneer sheet 42 is cut from flat veneer stockby laser cutting, die cutting, router cutting, or like process so as tohave the appropriate contour to cover half of a completed bat. Theveneer section 42 includes a narrow, longitudinally extending handlesection 44, a relatively wide barrel covering section 46 and a taperedsection 48, joining the two. One of the two veneer sheets used to formthe outer layer of the bat is preferably preprinted with a logo 50 whileit is flat. The logo is preferably imprinted with an epoxy ink by asilk-screen process, or branded by burning.

In the production of the bat, the plank 42 is preshaped into asemi-cylindrical configuration to create a preform generally indicatedat 52 in FIG. 7. To achieve this preform shape, the plank 42 issaturated with a liquid solvent such as water, alcohol or the like, isthen shaped into the semi-cylindrical form in either matched dies or onedie using a vacuum bag to pressure the plank 42 against the die, and theplank is heated to drive off the solvent. This process stretches thecellulose fibers of the veneer to achieve the semi-cylindrical shape 52.In alternative embodiments of the invention this preshaping step may beeliminated and the flat plank 42 may be shaped over the inner fabriclayers as part of the same process that bonds the outer layer to theinner fabric.

The fabric socks 24 are preferably formed by stacking several sheets offabric and cutting them into plank shape. A stack of three such "fabricplanks" 54a, 54b, 54c are illustrated in FIG. 8. Any number of sheetsmay be employed, but the preferred embodiment utilized stacks of foursheets. These fabric sheets may be woven or knitted or formed by otherprocess, such as by filament winding or poultrusion over the core ormandrel.

By appropriate choice of the nature of the layers, the stiffness,strength, flexibility and elasticity of the final bat may be controlled.The preferred composition creates a bat with such properties that whenthe ball impacts the bat during the batter's swing the bat undergoes alocalized deformation conforming to the contact area of the baseball, aswell as radial or hoop deformation (the cylindrical bat temporarilydeforms into an ovoid when viewed in cross section). It is importantthat foam core 28 be sufficiently resilient to allow this dualdeformation which aids in the transfer of the kinetic energy of theswinging bat to the baseball.

In another embodiment 70, shown in FIGS. 12 and 13, the core 28 isformed with a central cavity 29 which extends radially from thelongitudinal axis of the bat and longitudinally along a portion of thelength of the bat. The cavity 29 roughly underlies the "sweet spot" areaof the bat. It has the effect of increasing the hoop spring anddecreasing the local spring; i.e., bat 70 tends to deform more radially(into an oval) and less locally (thus producing the increased trampolineeffect) than bat 10. By adjusting the size and shape of the cavity 29,bat 70 may be designed for maximum energy transfer to the ball it hits.Furthermore, the cavity 29 may be fitted or partially filled with a plug31 formed of a different and generally less dense material to produce acomposite core. Adjustment of the configuration of the cavity 29 alsoallows more effective matching of the veneer, fiber fabric and coredensity and resiliency.

The embodiment shown in FIGS. 12 and 13 may be made so that the barrel72 is relatively larger than the handle 74 than is the case inconventional bats, without unduly increasing the weight of the bat. Abat of such design may be particularly useful in youth or trainingenvironments. Similar designs may also be employed in other productswhere balance and "natural feel" are important. Alternatively, the outercylinder and interior core may be formed so that no appreciabledeformation occurs upon impact with a pitched ball, in a manner similarto a solid wood bat.

In another embodiment 90 of the present invention, shown in FIG. 14, ahollow foamed in core 28 is provided with an internal layer of fiberreinforced resin 92. The resin layer 92 may be added by using a fibersock and arraying it over the mold on which the foam core 28 is formedor by adhering it to the interior of the foam core 28 after it isformed. This allows for a thinner core and results in a more resilientbat with a lot of hitting power, more so than an aluminum bat. In thisembodiment of the bat, the outer tube also elastically deforms toproduce oval distortion of the overall cylindrical configuration of thebat as well as the more localized deformation conforming to the contactarea of the ball.

It is important to note that cellulose material other than wood veneeror wood may be used as the outer layer of the bat. Paper or cardboardhaving a thickness in the range of 1/32-1/4 of an inch, especiallydecoratively treated to produce a visual woodgrain effect, for example,may be an effective alternative. Cellulose fibers tend to stretch whendeformed by the ball so as to impact over a number of fibers andtherefore exhibit high compressive strength. As a result, cellulosematerials are effective as the outer layer of the bat.

After two stacks of plank shaped fiber sheets of the type illustrated inFIG. 8 are created they are preferably sewn together along theirlongitudinal edges, preferably using a zigzag seamer or a butt-seameralong two lines 56, to form a cylindrical sock 24, generally illustratedin FIG. 9.

One alternate method of forming the bat, this sock 24 is arrayed over anappropriately shaped aluminum mandrel 60 which has been precoated with amold release compound. A second sock is then arrayed over the first sockwith its seams displaced by 90° relative to the seams of the first sock.Alternatively, the core may be pre-formed of foam or aluminum, and thesocks directly arrayed over the pre-formed core, thus eliminating use ofthe mandrel.

In an embodiment of the present invention, the fabric sock whichdirectly overlies the mandrel 60 employs inner layers formed of DuPontKevlar®, or S-2 glass fiber and three overlying layers of graphitefiber. The Kevlar® layer is preferably aligned with its fibers parallelto the longitudinal axis of the bat. The first graphite layer has itsfibers arrayed circumferentially, at 90° to the first layer, the thirdand fourth layers have their fibers arrayed at 45° to the fibers of thefirst two layers. The Kevlar® fabric is preferably K-49 type weighing11.6 ozs. per square yard and is 2160 denier, 41 ends per inch. Thethree graphite layers are of type 6K-T300 weighing 5.5 ozs. per squareyard and having 12.0 ends per inch. The four layers are preferablyknitted together with a thin sheet of polyester film which is markedwith the required plank pattern. These five layers are then cut togetherto form a plank.

A second sock is preferably formed of similar materials, but with alayer of fiber glass weighing 1 oz. per square foot, with its fibersarrayed circumferentially, overlying the outermost glass layer. Thesocks are sewn using Kevlar® K-49 thread with 12 needles per inch.

A pair of preshaped wood veneer planks 52 are then arrayed in matchedfemale molds 62 and 64. The interior surfaces of the veneer preforms 52are preferably coated with the liquid epoxy. The exterior, convexsurfaces of the preforms 52 may or may not be coated with epoxy beforetheir insertion in the mold 62, 64. The fabric socks 24 are alsothoroughly impregnated with the liquid resin, and the molds are thenclosed over the sock coated mandrel 60 or the pre-formed core, and thedies heated to thoroughly cure the resin. The resin used preferably hasa curing temperature in the vicinity of 300° F. The preferred resincomposition is Reichold 37127 epoxy. The resin may incorporate variousadditives such as natural rubber to improve the resiliency of thefinished bat.

After the resin is cured, the assembly of the wood veneer preforms 52and the sock 24 are removed from the molds 62, 64, and the mandrel 60,if employed, is removed from the barrel end of the tube. To form ahollow core bat, this tubular section may be finished by capping thehandle end with cap 14, joining the two by epoxy resin, and finishingthe barrel end by the cap 16, similarly adhered to the tube by epoxyresin. Alternatively, the caps 14 and 16 may be formed in the two part,matched female molds 62, 64 with the other components, the moldsincluding forms for molding the knob cap 14 and the end cap 16.

To form the embodiment of the bat with its foam core 28 shown in FIGS. 1and 2, the handle end of the bat may first be finished with the cap 14,as illustrated in FIG. 11, and the components of a self-foaming resininjected into the preform through a tube 66 inserted through a smallcentral hole in the open barrel end cap 16 which is later closed. Inthis method, the core is preferably a self-foaming urethane. Sufficientresin is injected to achieve a core density which may be in the range of10-30 pounds per cubic foot. The quantity of liquid resin injected alongthe length of the tube may be adjusted to achieve a varying densityfoam. Preferably, the density of the foam at the barrel end isrelatively high compared to the density adjacent the handle end toachieve a desirable end weighting.

Alternatively, the bat may be formed by using a pre-formed core ofurethane foam, or the like, formed in female split dies, instead of themandrel 60. For the embodiment shown in FIGS. 12 and 13, the pre-formingdies or molds may be designed so that the cavity 29 will be molded intothe core. As previously mentioned, it may be partially or entirelyfilled with a less dense material. The cavity may also be formed byhollowing out matching portions of two molded halves of the core so asto form a cavity when the halves are joined. A weight of a high densitymaterial such as lead, may be imbedded in the barrel end of the core 60to modify the weight distribution. The socks 24 are arrayed over thepreformed core and impregnated with liquid resin, and the veneerpreforms 52 are laid over the outer surface of the socks 24. The caps14, 16 are placed at the handle and barrel ends. The assembly ispreferably cured in matched female molds. Alternatively, it could becured in a vacuum bag placed within an autoclave. In this method offorming the bat, the curing temperatures for the resin can be limited toavoid damage to the foam core, limiting the strength of the finished batand increasing the curing time.

Rather than forming the fabric layers in the form of socks which areplaced over the mandrel, the fabric layers may be formed by filamentwinding techniques or by "pulltrusion" techniques known in the compositeart.

Having thus described my invention, I claim:
 1. A ball bat having abulbous end portion tapering to a narrow handle portion comprising:anelongated central core, extending substantially the full length of thebat; an inner cylindrical tube of fibrous reinforcement fabricimpregnated with resin, surrounding the core; and an outer tube formedof cellulose material, said cellulose material being coated andimpregnated with resin, and surrounding said inner tube and adheredthereto by said resins, wherein the combined thickness of said innercylindrical and outer tubes is substantially less than the diameter ofsaid elongated central core, at least in the vicinity of said bulbousend portion.
 2. The bat of claim 1 wherein said central core has acentral cavity extending along at least a portion of its length.
 3. Thebat of claim 1 wherein the tube of fibrous reinforcement fabricimpregnated with resin, surrounding the core, comprises at least oneelongated section of fibrous reinforcement fabric, includinglongitudinally continuous cords, extending the length of the bat.
 4. Thebat of claim 3 wherein said inner tube of fibrous reinforcement fabricimpregnated with resin, surrounding the core, further includes aspirally wound tape of fibrous reinforcement fabric overlying saidelongated section of fibrous reinforcement fabric and impregnated withresin.
 5. The bat of claim 1 wherein the outer surface of said tube ofcellulose material is decoratively treated to provide a visual woodgrainappearance.
 6. A baseball bat comprising a tube having a cylindricalouter layer of cellulose material overlying a cylindrical resinreinforced fiber layer formed of a plurality of sheets of fiber fabric,the fiber layer overlying a hollow core including a central cavityformed therein, the surface of the cellulose material overlying thefiber layer and each of said plurality of sheets of fiber fabric beingimpregnated with and adhered to one another with resin such that thecellulose material is bonded to the fiber layer with said resin.
 7. Thebaseball bat of claim 6 wherein said central cavity radially extendsfrom the longitudinal axis of the bat and longitudinally extends alongat least a portion of the length of the bat.
 8. The baseball bat ofclaim 6 wherein the central cavity is at least partially filled with amaterial of a different density than the density of the core.
 9. Thebaseball bat of claim 6, wherein an internal layer of fiber reinforcedresin is provided in said central cavity.
 10. The baseball bat of claim9 wherein the cavity extends from a barrel end of the tube for adistance along the length thereof.
 11. The baseball bat of claim 9 wherean internal layer of fiber reinforced resin is provided in said centralcavity.
 12. The bat of claim 9 further comprising a resin reinforcedfiber end cap disposed on a barrel end of said tube and adhered theretoby said resin.
 13. The baseball bat of claim 9 wherein the bat isconstructed such that, when a ball strikes the bat anywhere on itssurface but said sweet spot, the bat produces a stinging sensation whensaid handle end is gripped by a user.
 14. The bat of claim 9 wherein thecellulose material is paper.
 15. A baseball bat comprising a tubetapering from a relatively small cross-sectional handle and to arelatively large cross-sectional barrel end, the tube consisting of acylindrical outer layer of cellulose material overlying a cylindricalresin reinforced fiber layer formed of a plurality of sheets of fiberfabric and overlying a hollow core disposed within said tube anddefining a cavity in a region of the bat underlying a sweet spotcoinciding with a desired striking region on the surface thereof toprovide improved local deformation and radial deformation of said batupon impacting a baseball.